Various implementations of solid state lighting modules are known (for example flexible LED modules) in which the electrical and electronic components (light radiation source(s), resistors, capacitors, LED drivers etc.) are mounted on a single side of a board (e.g. similar to a Printed Circuit Board, PCB). In such implementations, all components therefore are located on the side which is visible to the end user, with possible disadvantages of various kinds.
For example, there may be limitations in the choice of the electrical and electronic components: if the number of such components is high, the radiation pattern may be uneven, with a consequent reduction of the device efficiency.
The electrical/electronic components are usually black or dark, and this colour may eventually produce visible black spots when the lighting module is off.
On the one side, it might be possible to ask suppliers to produce components with a white or other light colour package; this however might cause an increase in costs.
The drawback might also be limited by covering the dark components with a coating, for example a silicone coating, of a white colour, without covering the light radiation sources, also taking into account the fact that the sealing from the outer environment (IP protection) may be achieved with a two-step process:
a first step, in which the board surface is covered by e.g. a silicone layer, of a white colour, so as to cover the dark components, without covering the Light Emitting Surface(s) (LES);
a second step, in which the whole surface of the board (including what has already been covered with the white layer) is coated with a further transparent, i.e. light-permeable, layer (e.g. a silicone layer), so as to ensure an efficient light transmission while achieving an IP protection (Ingress Protection Rating) as well.
In order to simplify the process, and specifically the first step thereof, the light radiation sources (which must remain exposed) and the drive circuitry (which on the contrary must be covered and masked by a white layer) must not be present in too high a number.
Moreover, in various implementations, such a process may impose limitations in the choice of sources, e.g. because of the difficulty of using LEDs with high performance and reliability and low cost.
More generally speaking, another constraint may come from the fact that the LED-to-LED pitch is influenced by the space needed to mount the other electrical and electronic components.